Well, I made it all the way through calibrating my Tun and my Boil Kettle before the snow hit. I'm calibrating the Indoor Stove, now, but I think I'll wait until brewday before I go out and tackle the Propane Burner. (Hopefully New Years Day will be a bit warmer and drier)

I'll also have the oportunity, then, to see how well the calibration works. I'm crossing my fingers on the tun, because I'm used to hitting my Mash Temp spot on by preheating my Tun with the Strike Water. I'm still a little freaked out by trusting this to numbers like Heat Coefficients, but it will be more convenient, if it works...

If I hit my numbers, I'll post the values in the Database from my 5 gal. orange Rubbermaid cooler mash tun, which is probably a pretty common piece of kit. I'd be curious to see what other people get for values.

One thing I noticed is that I lost a lot more heat with 3 gallons of water sitting in the cooler than I do with 3 gallons of water and 10# of grain. I'm not sure if this is the lower total volume, the lost heat capacity of the grain, the cold day (in my kitchen it was only a bit above 60

I posted my 10-gallon Igloo calibration numbers in the Database for Equipment thread above a couple of weeks ago. I'm curious how my numbers compare to the Rubbermaid's. I now have a confession to make -- and I actually forgot I did this until I just saw slothrob's message (duh!). I, too, had an uncharacteristically large temperature drop between the 5 minute and 65 minute mark. I know from experience that in an hour's mash, I get a 1 to 2 degree drop at most. Chalking it up to an error on my part, I faked that temperature drop number to be just 2 degrees instead of the 16 or so it measured to be. That really makes the Schedule's rests' final temperatures much, much more accurate for me, so I know I was right do to that! Sorry for not remembering to report it here, though.

Having brewed several times since calibrating, I can say that my mash-ins have all been a few degrees too high. I'm thinking about tweaking my cooler's Heat Capacity a little to see if I can can get it to what works perfectly. Of course, doing so will mean that I will have completely abandoned my careful calibration measurements for real-life observations...

I think tweaking the numbers is the way to go, as you're essentialls adding replicate "calibration" data from your real world examples. I think a single calibration run probably has enough unaccounted for variables in it that you can't trust it to be the final word. My room temperature varied by 3

So if I was a degree high in the mash, would it mean that I should raise the temperature after 5 minutes of calibration by a degree to compensate?

That's exactly what I was thinking I will try. Doing that will lower the strike temp in the mash-in step by a little. I assume it will take a couple of brew sessions to work it out perfectly, but since it is pretty close already, I think I should be able to tune it in. By the way, allowing this minor tweaks in human-understandable terms (i.e., adjusting calibration measurements rather than guessing how many "J/kg K" units to add/subtract to/from the Heat Capacity) is yet another excellent feature of this software!

After some delays I finally got a chance to test my calibration an a fine spring day in January ( ).

The day was so warm that I ended up being able to run my mash at the same temperature at which I calibrated.

The heat loss during mash was close to that predicted by BTP (Note: this was a reletively small beer, so there was only 8.5# of grain and 3 gallons of water in the mash). I lost 1 degree less than predicted, but my previous data suggests that this is more than I lose when the tun is closer to full. For now, I think I'll adjust the calibration data point up 1 degree for that lost from 5 to 65 minutes.

While brewing today, I was very careful with my mash-in measurements to be as accurate as I could manage, so that I could use them to retrofit the Mash-In step with what actually happened. In other words, as discussed above, my plan was to tweak my cooler mash tun vessel's "Temp after 5 minutes" to make BTP calculate the strike temperature that I actually used today. Theoretically, it would be the perfect calibration to allow BTP to calculate all future strike temperatures accurately. Or so I thought...

Long story (kind of) short, real life today took 166.5 degree water and hit a 154 mash. But when I now try to make BTP come up with a 166.5 Strike Temp by editing my vessel's Heat Capacity for today's session, I can't make it work. Even if I say there was no heat loss at all after 5 minutes in my vessel calibration, the Strike Temp calculated in the schedule is still too high (167.4). I found that if I change my vessel calibration to say that the water increased by one degree after 5 minutes, then the Strike Temp is accurate enough (166.7). But that can't be right!

It has been a long brew day, so maybe I'm not thinking clearly enough right now. I'm sure I measured everything (grains, water, temperatures) as accurately as I could. Is my logic off? Has anyone else tried this approach, yet?

Brant wrote:It has been a long brew day, so maybe I'm not thinking clearly enough right now. I'm sure I measured everything (grains, water, temperatures) as accurately as I could. Is my logic off? Has anyone else tried this approach, yet?

A couple things that may be influencing the results. Grain temperature can play a part. Also, BTP currently assumes the vessel is at room temperature (around 68F) which may not be the actual vessel temperature. Ambient air temperature is a setting that will be included on a per session basis in a future update. This will likely help make results more accurate; and the lack of this setting can easily lend to the inconsistency.

Thanks, Jeff. You just answered one of my biggest questions. I had been assuming that ambient, tun, and grain temperatures were all supposed to be the same temperature, and that that was the temperature I needed to enter in the "Grist Temp" field on the Mash-In. In fact, to hopefully remove the variable of inconsistent grain and vessel temperature, I rested the dry grains in the cooler for about half an hour, with the lid closed, before adding the strike water, thinking the grains and the vessel would be the same temperature. Taking reading in several places in the grain, it was between 62 and 63.5, so I entered 63 in the Grist Temp field, which was ambient before I started brewing. I brew in my garage, and store both my grains and my equipment there, so they are already equalized. The burner heats the ambient temperature by about 10 degrees quickly when I start, though. I thought by isolating the grain and the cooler (by putting the lid on), I could remove the variable of the increasing ambient temperature.

Is it possible that the 73 or so ambient temperature when I poured in my strike water caused my inaccuracy? My guess is that by pouring in strike water, I'd be losing a little heat from it before it even hits the grains (does BTP take that into account? I'd guess that it cannot, so no), and that the temperature of the grains and cooler would greatly outweigh the air temperature which rose from the low sixties to the low seventies during the previous 15 minutes or so. It just seems to me that if the my cooler was 63 degrees, and BTP is calculating it to have been 68 degrees, then wouldn't that have made my mash temp hit even higher than target? Or am I not giving enough credit to the ambient temperature's affect?